Isobutylene–isoprene rubber/layered silicate nanocomposites prepared using latex method: Direct casting versus melt mixing after coagulation

In this study, polymer nanocomposites of isobutylene–isoprene rubber blended with sodium–montmorillonite were prepared using latex and co-coagulating methods and their influence on thermal, mechanical, and gas barrier if isobutylene–isoprene rubber composites were compared. The dispersion of the layered silicates in the matrix of the obtained nanocomposites was investigated using transmission electron microscopy and X-ray diffraction. The transmission electron microscopy images revealed both partially exfoliated and intercalated structures for the isobutylene–isoprene rubber/montmorillonite nanocomposite prepared using the latex method and a purely intercalated structure for the sample prepared using the co-coagulating method. The surfactant used in the latex method played an important role in determining the interlayer distance within the silicates in the isobutylene–isoprene rubber/montmorillonite composites, in which the interlayer d-spacing in the silicates increased relative to that for the co-coagulating method after the curing process. The tensile and thermal properties of the isobutylene–isoprene rubber/montmorillonite nanocomposites improved with respect to those of the neat isobutylene–isoprene rubber. The tensile strength and decomposition temperature of the isobutylene–isoprene rubber/montmorillonite composites (5 parts per hundred resin (phr) montmorillonite blended with latex) increased by 100% and 20℃, respectively. The gas-barrier properties of the obtained composites (10 phr montmorillonite blended with latex) even increased by 60% compared with those of the neat isobutylene–isoprene rubber. For the isobutylene–isoprene rubber/clay composites prepared using the co-coagulating method, an observable improvement of the tensile properties was achieved only if the content of the blended clay was greater than 10 phr.